20 Chapter 2 Abstract The objective was to define the relationship between histopathologic changes after pre-operative chemo-radiotherapy (CRT) and clinical outcome following tri-modality therapy in patients with superior sulcus tumors. A retrospective analysis of tumour material was performed in a series of 46 patients who received tri-modality therapy between 1997 and 2007. Median follow-up was 34 months (5 – 154). Pathologic complete response (pCR) was present in 20/46 tumors (43%). The most common RECIST score after CRT in patients with pCR was a partial response (PR; 10/17, 3 unknown) whereas in patients without a pCR, stable disease was the most common (22/26) (p=0.002). In 26 specimens with residual tumour, this was mainly located in the periphery of the lesion rather than the center (Spearman’s correlation - 0.67, p<0.001). Prognosis was significantly better after a pCR compared to residual tumour (70% 5-years overall survival vs. 20%; p=0.001) and in patients with fewer than 10% vital tumour cells as compared to those with >10% (65% 5-years overall survival vs 18%; p<0.001). A low mitotic count was associated with a longer disease-free survival (p=0.02). Complete pathological response and the presence of fewer than 10% vital tumour cells after preoperative CRT are both associated with a more favorable prognosis. A modification of the pathological staging system after radiotherapy, incorporating the percentage of vital tumour cells, is proposed.
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